Build PDF through Nix + Deploy to Github Pages

[srid]

• Add a flake.nix => can use nix build to build the PDF locally.
• This PDF in turn is deployed to Github Pages via Github Actions.

The PDF built in CI for this PR can be found here: https://srid.github.io/DaoFP/DaoFP.pdf

Once merged, the generated PDF will instead by available at https://BartoszMilewski.github.io/DaoFP/DaoFP.pdf (assuming Github Pages is enabled in the repository settings).

Things to do:

• Figure out why ToC is missing from the PDF

Eventually, we can add a package for building the ePub too; #9

[srid]

@BartoszMilewski This PR is ready. It generates the PDF in CI and then deploys them to GitHub Pages. If you merge this PR and enable "GitHub Pages" (pointing to the gh-pages branch; see screenshot below) in repository settings, the PDF will be available at https://BartoszMilewski.github.io/DaoFP/DaoFP.pdf ... and it will automatically update (within ~5-10 minutes) as you push commits to the master branch.

Let me know what you think. Support for ePub can be added on top separately.

[madnight]

@BartoszMilewski Any updates on this? I'm particularly interested in an epub version of DaoFP similar to the epub version of "Category theory for programmers".

[BartoszMilewski]

I don't feel like the book is ready for that. I'm still rewriting chapters, and I only push the changes when I have something solid.